This invention relates generally to fiber board and more particularly to a ceramic fiber board having superior green strength at low density.
Ceramic fibers are widely used in the fabrication of blankets, felts and boards for high temperature insulation. Typical applications for fiber boards include, but are not limited to steel splash boards, oven or furnace linings, casting setters or casting tips.
These fiber boards may contain non-crystalline aluminosilicate fibers, crystalline high alumina fibers or a mixture of the two types of fibers. The fibers are usually formed into boards by vacuum casting or other continuous casting methods such as Fourdrinier or rotoformer in which a slurry of fibrous material and various binders and fillers is drained through a screen resulting in a felted pad which is then dried to yield a rigid board.
High strength ceramic fiber boards have a green strength exceeding 300 psi. These boards generally have a green density of at least 22 lb/ft.sup.3. In order for conventional high strength fiber boards to be machinable in, for example, sawing, lathe turning, or die cutting operations without significant breakage, tearouts or generation of fiber dust, the green density of the board must be at least 30 lbs/ft.sup.3. These higher density boards are generally more costly and more difficult to handle in large pieces without breakage.
Accordingly, it is a primary object of this invention to provide a high strength ceramic fiber board having a density less than 22 lbs/ft.sup.3.
It is a further object of this invention to provide a high strength fiber board having a resistance to breakage when handled or machined at a density less than 30 lb/ft.sup.3.